An electronic product internally includes electronic elements that would produce a lot of heat during operation thereof. In the event the electronic elements are always in a high-temperature state, they will have lowered operating efficiency or even become burned-out. To protect the electronic elements from poor operating efficiency or burnout, at least a heat dissipating unit, such as a radiating fin assembly or a heat sink, and a fan are usually used together to dissipate the heat produced by the electronic elements, so as to prolong the service life of the electronic elements.
Conventionally, to enable convenient assembling of a fan, the bearing of the fan is associated with the bearing cup by way of loose-fit, and the rotary shaft of the blade assembly of the fan is also loosely fitted in the central hole of the bearing. While the loose-fit between the bearing and the bearing cup enables quick assembling of the fan, the bearing will vibrate relative to the bearing cup and produce noise during the operation of the fan.
To overcome the problem of vibration the bearing relative to the bearing cup, there are generally two ways to retain the fan bearing in place in the bearing cup. The first way is to injection mold the bearing and the bearing cup at the same time using plastic materials, and the second way is to manufacture the bearing and the bearing cup with metal materials and assemble them by way of tight-fit. The second way provides higher fitting accuracy between the metal bearing and bearing cup, but requires higher machining cost.
On the other hand, the forming of the bearing along with the bearing cup through plastic injection molding as suggested in the first way can be achieved at lower cost but it provides only relatively lower fitting accuracy between the bearing and the bearing cup. That is, a too tight fitting of the bearing in the bearing cup tends to cause bore shrinkage of the bearing, while a too loose fitting of the bearing in the bearing cup fails to effectively retain the bearing in place in the bearing cup.
In brief, the prior art bearing retaining structure for fans has the following disadvantages: (1) having poor fitting accuracy between the plastic injection molded bearing and bearing cup; (2) requiring higher cost to manufacture metal bearing and bearing cup with higher fitting accuracy between them; and (3) the assembled plastic bearing and bearing cup tending to produce vibration and noise during fan operation.